tamerlan was charged in cambridge with beating his former girlfriend. he started posting violent videos. >> that's why he was demonized. >> he began writing bazaar tweets. a decade in america already, i want out. authorities never saw this coming. investigators are asking this morning, are there more cell members out there? that's the critical question, dan and bianna. >> and pierre, when you talked to your sources, do you sense a high level of concern that there may be co-plotters out there? >> dan, i think they are trying to find out are there more people out there? so critical they talk to the younger brother who's still recovering from the injuries. they say they must find that out as quickly as possible. there's an international investigation under way to get to that subject. >>> time is of the essence, so let's bring in george stephanopoulos, host of "this week." good morning, george. i want to show a picture, are they forced now to consider launch a military response? if in fact these brothers are connected to an international plot? >> i think th